1. Field of the Invention
The present invention relates to a liquid composition, an ink set, a recording process, an ink cartridge, a recording unit, a process for forming a multi-color image, an ink-jet apparatus, a process for facilitating fixing of inks to a recording medium, and a process for improving the quality of a multi-color image.
2. Related Background Art
Inks using carbon black, which is a black colorant capable of providing prints high in optical density and excellent in fastness properties and the like, have heretofore been proposed as a black ink for writing utensils (fountain pens, felt-tip pens, aqueous ball-point pens, etc.) and black ink for an ink-jet apparatus.
In particular, in recent years, detailed research and development have been conducted of various aspects such as the composition and physical properties of ink so that a good print can be made even on plain paper, such as paper for copying, paper for reporting, notepaper, letter paper, bond paper and continues slip paper, which are commonly used in offices. For example, Japanese Patent Application Laid-Open Nos. 61-283875 and 64-6074 disclose water-based pigment inks comprising carbon black and a dispersing agent. Japanese Patent Application Laid-Open No. 8-3498 points out such a technical problem that when an ink containing carbon black together with a dispersing agent is used as an ink for an ink-jet printer, ejection becomes unstable or a sufficient image density is not achieved, and discloses a water-based pigment ink using self-dispersing carbon black, but using no dispersing agent as an ink capable of solving such a problem.
Dyes are used as coloring materials in color inks. Dyes are superior in coloring ability and stability, but are required to be improved in water resistance and light resistance. In recent years, a great number of water-based inks using an organic pigment in place of a dye have been proposed for solving these problems. For example, Japanese Patent Application Laid-Open No. 9-40898 discloses an idea that a high-hydrophilic, low-molecular compound is adsorbed on the surface of an organic pigment, and shelf stability and the quality of printed images are made to be compatible with each other. In addition, a dispersion of an organic pigment is disclosed in U.S. Pat. No. 5,837,045, etc, where the organic pigment has functional groups bonded directly to its surface, like carbon black, many types of which have been proposed, capable of being stably dispersed or dissolved in water without using any dispersing agent. The present inventors have carried out various investigations as to the case where inks containing a coloring material, such as carbon black and/or an organic pigment, were used in ink-jet recording. As a result, it has been found that when the compositions of the inks are adjusted in order for the inks not to penetrate into a recording medium as much as possible for the purpose of improving image density and coloring ability, the inks remain on the recording medium without penetrating into the recording medium, and so bleeding (hereinafter singly referred to as xe2x80x9cbleedxe2x80x9d) between different colors occurs at their boundaries as a new problem caused by lowering the penetrability.
In order to prevent the occurrence of bleed, for example, Japanese Patent Application Laid-Open No. 6-228478 discloses a technique in which an ink set comprising a colorless liquid composition and an ink is used, and the two react with each other through ionic reaction when mixed with each other so that the viscosity of the ink is increased or a coloring material in the ink is coagulated or deposited so as to facilitate the separation (solid-liquid separation) of solids (the coloring material and the like) from a liquid in the ink on a recording medium.
The occurrence of bleed can be extremely effectively prevented by using the above-described technique. However, since the technique utilizes an ionic reaction, the above ink and liquid composition quickly react with each other when they are mixed. Accordingly, when such a combination is used as, for example, an ink set for ink-jet recording, recovery systems for the ink and liquid composition in an ink-jet head must be completely separated. More specifically, when the recovery systems for the ink and liquid composition are made common, the ink and the liquid composition react with each other in such a recovery system to solidify the components in the ink. As a result, the function of the recovery system in the ink-jet head may be gradually deteriorated. On the other hand, the provision of a plurality of recovery systems in an ink-jet apparatus may inhibit the apparatus from being miniaturized or cause an increase in product cost in some cases.
The present invention has been made in view of the foregoing circumstances and one of its objects is to provide a liquid composition which can realize high-quality images at a low cost.
Another object of the present invention is to provide an ink set which enables high-a-quality images to be formed.
Still another object of the present invention is to provide a recording process which enables high-quality images to be formed.
A further object of the present invention is to provide a process for forming a high-quality, multi-color image, which can prevent bleed from occurring.
A still further object of the present invention is to provide a recording unit and an ink cartridge which can be used in the formation of high-quality images.
Yet another object of the present invention is to provide an ink-jet recording apparatus which enables high-quality images to be formed.
Yet still another object of the present invention is to provide a process for facilitating the fixing of an ink to a recording medium to form a high-quality image.
A yet still further object of the present invention is to provide a process for improving the quality of a multi-color image by preventing the occurrence of bleed.
The above objects can be achieved by the present invention described below.
According to an embodiment of the present intention, there is provided a liquid composition used for forming an ink-jet image together with an ink containing a coloring material dispersed in an aqueous medium by the action of an ionic group, which contains at least one salt selected from the group consisting of (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3, wherein M1 denotes an alkali metal, ammonium or organic ammonium, and Ph denotes a phenyl group.
According to an embodiment of the present invention, there is also provided an Ink set comprising, in combination, an ink comprising an aqueous medium and a coloring material dispersed in the aqueous medium by the action of an ionic group, and the liquid composition described above.
According to an embodiment of the present invention, there is further provided a recording process comprising the steps of:
(i) applying an ink comprising an aqueous medium and a coloring material dispersed in the aqueous medium by the action of an ionic group to a recording medium; and
(ii) applying a liquid composition containing at least one salt selected from the group consisting of (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3, wherein M1 denotes an alkali metal, ammonium or organic ammonium, and Ph denotes a phenyl group, to at least a region on the recording medium, to which the ink is applied.
According to an embodiment of the present invention, there is still further provided a process for forming on a recording medium a multi-color image including regions which are different in hue from each other and have a portion at which they are adjacent to each other, the process comprising the steps of:
applying a plurality of inks different in hue from each other to the recording medium to form the multi-color image, wherein at least one of the inks is a coloring material-dispersed ink containing an aqueous medium and a coloring material dispersed in the aqueous medium by the action of an ionic group; and
applying a liquid composition containing at least one salt selected from the group consisting of (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3, wherein M1 denotes an alkali metal, ammonium or organic ammonium, and Ph denotes a phenyl group, to at least a region on the recording medium, to which the coloring material-dispersed ink is applied.
According to an embodiment of the present invention, there is yet further provided a recording unit comprising a liquid composition holding portion holding a liquid composition containing at least one salt selected from the group consisting of (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3, wherein M1 denotes an alkali metal, ammonium or organic ammonium, and Ph denotes a phenyl group, and an ink-jet head from which the liquid composition is ejected.
According to an embodiment of the present invention, there is yet still further provided a recording unit comprising a liquid composition holding portion for holding a liquid composition containing at least one salt selected from the group consisting of (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3, wherein M1 denotes an alkali metal, ammonium or organic ammonium, and Ph denotes a phenyl group, an ink-jet head from which the liquid composition is ejected, an ink container portion holding an ink containing an aqueous medium and a coloring material dispersed in the aqueous medium by the action of an ionic group, and an ink-jet head from which the ink is ejected.
According to an embodiment of the present invention, there is yet still further provided an ink cartridge which holds a liquid composition containing at least one salt selected from the group consisting of (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO2 and (M1)2CO3, wherein M1 denotes an alkali metal, ammonium or organic ammonium, and Ph denotes a phenyl group, and is detachably installed in an ink-jet head from which the liquid composition is ejected.
According to an embodiment of the present invention, there is yet still further provided an ink-jet apparatus comprising a liquid composition holding portion holding a liquid composition containing at least one salt selected from the group consisting of (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3, wherein M1 denotes an alkali metal, ammonium or organic ammonium, and Ph denotes a phenyl group, an ink container portion holding an ink comprising an aqueous medium and a coloring material dispersed in the aqueous medium by the action of an ionic group, and ink-jet heads from which the liquid composition held in the liquid composition holding portion and the ink held in the ink container portion are ejected independently of each other.
According to another embodiment of the present invention, there is yet still further provided an ink-jet apparatus comprising a first recording unit which comprises a liquid composition holding portion holding a liquid composition containing at least one salt selected from the group consisting of (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3, wherein M1 denotes an alkali metal, ammonium or organic ammonium, and Ph denotes a phenyl group, and an ink-jet head from which the liquid composition is ejected, and a second recording unit which comprises an ink container portion holding an ink comprising an aqueous medium and a coloring material dispersed in the aqueous medium by the action of an ionic group, and an ink-jet head from which the ink is ejected.
According to an embodiment of the present invention, there is yet still further provided a process for facilitating the fixing of an ink containing an aqueous medium and a coloring material dispersed in the aqueous medium by the action of an ionic group to a recording medium when the ink is applied to the recording medium by using an ink-jet apparatus, the process comprising applying a liquid composition containing at least one salt selected from the group consisting of (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3, wherein M1 denotes an alkali metal, ammonium or organic ammonium, and Ph denotes a phenyl group, to at least an area on the recording medium, where the ink is applied.
According to an embodiment of the present invention, there is yet still further provided a process for improving the quality of a multi-color image on a recording medium, the multi-color image containing at least a first region and a second region which are different in color from each other and adjacent to each other at least at a part thereof, the process comprising the steps of:
forming the first region by a process comprising a step of applying a first ink having a first hue to the recording medium and a step of applying a liquid composition to at least an area on the recording medium, where the first ink is applied; and
forming the second region by a process comprising a step of applying a second ink having a second hue to the recording medium,
wherein the first ink is an ink containing an aqueous medium and a coloring material dispersed in the aqueous medium by the action of an ionic group, and the liquid composition contains at least one salt selected from the group consisting of (M1)2SO4, CH3COO(M1), Phxe2x80x94COO(M1), (M1)NO3, (M1)Cl, (M1)Br, (M1)I, (M1)2SO3 and (M1)2CO3, wherein M1 denotes an alkali metal, ammonium or organic ammonium, and Ph denotes a phenyl group.
According to the above embodiments of the present invention, for example, image quality can be improved. More specifically, even when printing is conducted on paper having high permeability, with which, for example, character sharpness may be impaired, or image density and coloring ability may be deteriorated, high quality images can be formed, and moreover the fixing ability to the paper can also be improved.
According to the above embodiments of the present invention, the occurrence of bleed can be extremely effectively alleviated in addition to the effects described above, and so high-quality, multi-color images can be provided.
The reason why the above effects are brought about by such embodiments is not clearly known, but is guessed to be as follows.
Namely, when the liquid composition is applied to a recording medium, a solvent in the liquid composition penetrates into the recording medium or vaporizes into the air, and so the concentration of the salt in the liquid composition on the surface of the recording medium quickly increases. When the liquid composition that causes such a phenomenon and an ink in which a coloring material such as a pigment is stably dispersed by the action of an ionic group, for example, an anionic group, are applied to the recording medium in such a manner that they are brought into contact with each other on the surface of the recording medium, the dispersion stability of the coloring material in the ink is broken by the increase in the concentration of the salt in the liquid composition on the surface of the recording medium, and so the coloring material comes to aggregate or deposit. In other words, the separation of the coloring material making up the ink and the aqueous medium are facilitated. As a result, the penetration of the coloring material into the recording medium can be prevented and images excellent in sharpness of contour and the like can be formed. In addition, it is considered that since the ink quickly undergoes solid-liquid separation, it is difficult for such a phenomenon as described above to occur even when printing is conducted on paper having high permeability. In other words, it is considered that factors depending on the kinds of paper, such as the degree of permeability, come to hardly matter. Further, the liquid composition and ink according to the present invention do not immediately react with each other when mixed as described above. Therefore, they have such an advantage that even when they are used as, for example, an ink set for ink-jet recording, a common recovery system of an ink-jet head can be used.